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This paper is a continuation of an earlier overview on the subject and presents the results of a sensitivity analysis that assessed the ability of the new design guide to portray the impact of temperature and moisture content on flexible pavement performance. The study used the most common asphalt concrete (HL3) and unbound materials (granular A and silty sand) used in Canada. Two binders [performance grade (PG) 52-34 and PG 58-28] and three moisture conditions (dry, wet, and optimum) were chosen. Designs performed using Level 3 analysis for unbound materials and Level 1 for asphalt concrete showed that the new design guide is sensitive to binder performance grades and climatic zones (cold versus warm); however, the new design guide showed limited sensitivity to the state of unbound materials: permanent deformation showed negligible changes between wet, dry, and optimum conditions. Model simulations indicated that rutting that accumulated throughout the 20-year design life for the warm region (Long Beach, California) was 50% more than that in the relatively cold region (New York). Using different soil conditions for unbound materials showed that the increase in resilient modulus from wet to dry conditions increases total rutting by 27%. Results also demonstrated good sensitivity to the type of asphalt binder and agreed with the binder type objective: the HL3 mix prepared with the PG 58-28 binder substantially decreased rutting (by 271%) compared with the mix prepared with the PG 52-34 binder. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the effects of environmental factors, namely moisture and temperature, on the material properties of flexible pavement road structure considered in the design guides of AASHTO. It considers the historical development of AASHTO design guides with new design guides. The study showed the shift in emphasis from total reliance on an empirical method to a combination of mechanistic and empirical methods in the new design guide. Further, moisture and temperature were indirectly considered in the current guide, whereas these parameters are accounted for in the new design guide through the resilient modulus and the complex modulus. The sensitivity analyses of environmental consideration using the new design guide software are presented in this paper. [ABSTRACT FROM AUTHOR]